Mercedes-Benz Forum banner

722.422

4K views 16 replies 4 participants last post by  Ivanerrol 
#1 ·
February 5th I changed out the fluid and filter in my 722.422 transmission in my '96 C200. - 259,000 kilometres
I used 236.10 synthetic fluid. This car had been serviced at the dealership previous to my ownership (up to 200,000 kilometres) so They had used synthetic for previous fluid changes.

Febuary 20 i was stopped at a traffic light on a flat road. On moving off I heard a slight "clung" the transmission kicked a bit however moved off and the gear changes were quite good

February 22 I was stopped at traffic lights going up a steep hill. Went to move off - engine raced but no forward movement. Manually shifted the gear lever into first gear and the car slowly moved off. Checked the fluid level - it seemed a little low so topped up with a litre of fluid. Made some improvement but still not good.

Managed to get the car back to my garage. drained 4 litres of fluid out - rather cloudy black and burnt smelling.
here's an image of the fluid I installed 3 weeks ago on the left with the withdrawn fluid on the right.


I suspect some clutches have been damaged.

I have bought some mineral DexIII.
I might drain the current fluid, change the filter and fill up with mineral fluid to see if this fixes the problem - I'm not overly optimistic.

Failing that I have access to a second hand 722.423 with only 55,000 kilometres on it.

Anyone care to comment?
 
See less See more
1
#2 ·
Opened up the pan and found these.

I assume they're the B2 pin and holding washer.

Can these be reinstalled without removing the entire transmission or indeed without pulling the transmission apart?
By reinstalling I mean that I will need to source new bits from the dealership.
 
#3 · (Edited)
These bits are from the B2 piston - I have discovered from Benzworld forum posts from back in 2008 - 2011.

This is a DIY fix - if you have the appropriate tools and sufficient skill set.

First issue is to see if I can still source the required bits and pieces from M.B.

The Pan needs to come off and the valve bodies removed to do this job.
The B2 piston needs to come out from the side of the transmission.
I'll try and do with the tranny still in the car otherwise I'll need to get it out.

Unfortunately this is a RHD C200 with a specific 722.422 transmission - something that was never released in the U.S. - Closest being a C230 with a 722.423. Most likely different piston pins between the 722.422 and 722.423
 
#4 ·
Here's a diagram with the offending parts - 25 and 20

I am going to try and reinstall new bits without removing the tranny from the car and removing the B2 piston.
Here's where it needs to go.


I cant get that yellow frame out so it might be a struggle. I've seen a write up on the Porsche forum where this job has been done with the tranny in the car but had the B2 piston removed as well as that yellow plastic piece.

The Pin and retainer were less than $30 Ozzie dollars at the dealership.

here's a image of the brake band and the B2 piston pin.
 
#8 ·
I assuming the plastic retaining clip failed through aging brittleness and the pressure being applied to the brake band caused it to come out.

On doing a goggle search I found this to be reasonably common. Even a few threads about this very same issue on this forum dating back more than 10 years.
Certainly common on the Porsche forums where the 928 used the 722.3 tarnny.
 
#9 · (Edited)
The pin fell out because the retaining plastic clip fractured because of brittleness due to age.
here's the new pin and retainer next to the old.


It was necessary to get the yellow plastic holding frame out to get the new pin and retainer in.
It took me at least three hours of struggling upside down on my back underneath the car before I realized either the transmission had to be lowered to remove the B2 piston and Pin or remove the transmission altogether and do this on the bench. In the end I struggled and removed the yellow part.


I then realized the MB diagram is a little misleading. The retainer doesn't go on the brake bad side.

here it is installed - pin in and retainer in place.


Now to put the transmission back together.

To be continued.
 
#10 ·
Well this is super familiar territory my friend :)

http://www.benzworld.org/forums/w202-c-class/2302322-722-4-transmission-brake-band-piston.html

and eventually

http://www.benzworld.org/forums/w202-c-class/2732889-mercedes-benz-722-4-transmission-brake.html

Whats going on with your transmission at least on the pin - is that the friction material on the brake band is diminished and the pin is slipping. You will want to install a longer pin not one with the same size, although if you did so already no big deal. But expect it to fall out again, and expect to lose forward engage and drive home 1 mile in reverse like I did (yes I am retarded.)

Eventually you will want to replace the brake band.

Bad news is that takes the transmission out of your car.
Good news is that it is way easier to work on it when it is out.
Good news is you get inspect your clutches and see if there is any friction material left and replace those at the same time.

A brake band is going to cost 180 if you can find it. Anything less than that is a good deal in my opinion.

Feel free to PM me your phone number and I'll call you, I have been all over this subject. jimmyhsiung and MAVA on this forum, amongst several others are super helpful / geniUS guys on this subject.
 
#11 ·
I realized you are in Australia and I can't call you :) But if you have skype we can do that too. Best wishes on the NBN rollout there, hope it makes your internet faster!
 
#16 ·
It's not that hard, it just takes time more than anything. It was very intimidating at first but it really made my admiration for the engineering of these vehicles increase.

Ivan -

Usually that is caused by a pressure issue on the vacuum lines, but it sounds like you double checking the connections did the trick. Also friendly reminder, when you take fluid out and put it back in, cycle through all the gears for about 15 seconds each once or twice before actually moving forward.

I really hope this doesn't happen to you, but especially since you didn't put a bigger pin in, I estimate 100 miles before it falls out again. Again, I HOPE I am wrong. I just feel like I am watching a video of myself here. That pin is not supposed to fall out, and its a symptom not a cause. I would drive not too far from home and avoid anywhere you can't get a tow.

If you like the car, I'd get that 2nd transmission for 300, especially if the body is nice and you like it. Taking the engine out and putting on a new transmission is not that hard believe it or not.
 
#14 ·
Update.

Put the transmission back together and it seems either I've missed something or put the valve body back in incorrectly.

Car now moves forward in first - but that's all we get. Doesn't change up to second, third etc.

I'll need to check the valvebody install.

Failing that - it's a replacement tranny.
 
#15 ·
Update II.

Methodically went through all the scenarios that could cause a transmission to stick in first gear. Checked through forum posts and other info on line.

Checked the Bowden cable, kick down switch.
Checked the fluid level again - topped up another 750ml - it was full previously.

Started car shifted gears between first and reverse up and down a few times.

Went for a drive.

Transmission changing beautifully :eek

Drove it in stop start traffic and then a spin up the freeway.
Smooth changes and quiet.

All Good - so Far.

Bearing in mind what Stig has mentioned above. - The fix might only be temporary. I'll either consider installing another transmission or at worst case put this car on the market and find another.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top